Generally, on a product assembly line, in order to reduce the number of vehicles required at the time of conveying and stocking the components, or to save spaces to be occupied by boxes of the components, components conveyed from a supplier or a preceding step are delivered in what is called a bulk package in many cases.
Thus, in order to promote automation of product assembly, positions and orientations of components to be supplied to an assembly apparatus need to be aligned with some means.
Hitherto, as means for automatically aligning bulk components, there has been widely used dedicated component alignment devices called parts feeders. However, the parts feeders are exclusively designed in accordance with types of the components, and hence have no versatility. Thus, there are problems of requiring a long design time, being expensive, generating vibration and noise during an operation, and occupying a large proportion of a floor space in a factory.
Further, when the components have complicated shapes, there is another problem in that the components are entangled in the parts feeder, and temporary operation stoppages called work interruptions may occur. As a result, calls to maintenance personnel may be more frequently made.
Still further, depending on shapes, the components may not be aligned by the parts feeder. Thus, in such a case, the parts feeder itself cannot be used.
Under the circumstances, as an automated method that can be used instead of the parts feeder, there has been known a technology of correcting positions and orientations as follows. The bulk components are brought into a state in which the components are not overlapped with each other to some extent with some hardware mechanism, and then only components in preferred orientations are recognized with a vision sensor (for example, refer to Patent Literature 1).
In addition, there has been known a technology of recognizing positions and orientations of the bulk components, changing an orientation of a picked-up component when necessary and temporarily placing the picked-up component, and re-changing, when necessary, the orientation of the picked-up component to align the picked-up component (for example, refer to Patent Literature 2).
The technology described in Patent Literature 1 depends on a probabilistic phenomenon in which only components in preferred orientations are selected and handled from among a sufficient number of components supplied in advance. Thus, a proportion of the components in preferred orientations becomes lower along with a decrease in number of the components. As a result, there arises a problem in that the calls to maintenance personnel are more frequently made irrespective of a state in which a certain number of components are left.
Further, when components that are less likely to have preferred orientations are supplied as objects, a larger number of components need to be supplied in advance. Thus, there arises a problem in that much stock needs to be kept on hand, and a space volume (floor space and height) in a factory is wasted.
Meanwhile, the technology described in Patent Literature 2 is devised for cubic components against which a suction pad can be accurately brought into abutment without involving air leakage and which can be sucked in an intended way. Thus, there arises a problem in that the technology described in Patent Literature 2 cannot be adapted to components that are not provided with parts to which the suction pad is ineffective or that cannot be sucked by the suction pad, such as a component having a planar shape, a component having a complicated shape, a component having surfaces with projections and recesses, a porous component, and a component having a narrow shape.
Note that, when the suction pad cannot be used, suction with a blower may be performed. However, in this case, there are problems of loud noise and high electric power consumption.
In addition, in each of the cases of Patent Literatures 1 and 2, hands that are specially designed in accordance with types of the components are used to absorb significant errors that may cause failures in final alignment. Thus, components of a plurality of types cannot be aligned with a hand of a single type, and hence it is necessary to prepare hands as many as the types of the components. As a result, there arises a problem in that time periods for switching the hands and a large space for temporarily placing the hands are required.
Further, the hands need to be re-designed in accordance with the types of the components, and hence there arises a problem in that, at the time of changeover of production equipment, costs for re-designing the hands (design cost, production cost, and adjustment cost) are required.